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Prolonged retention of doubly labeled phosphatidylcholine in human plasma and erythrocytes after oral administration
Author(s) -
Galli Claudio,
Sirtori Cesare R.,
Mosconi Cristina,
Medini Lucia,
Gianfranceschi Gemma,
Vaccarino Viola,
Scolastico Carlo
Publication year - 1992
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02535580
Subject(s) - phosphatidylcholine , chemistry , choline , chromatography , blood plasma , oral administration , red blood cell , isotope , clinical chemistry , high performance liquid chromatography , biochemistry , endocrinology , phospholipid , biology , physics , quantum mechanics , membrane
The plasma kinetics of a preparation of dilinoleoyl phosphatidylcholine (DLPC) specifically labeled with 3 H in the choline moiety and with 14 C in the 2‐fatty acid (FA) were evaluated in six healthy volunteers after oral administration. Retention of both isotopes in plasma exceeded expectations, with a half‐life in the elimination phase of 172.2 h for 3 H and 69.7 h for 14 C. Up to 60 d after administration, there were still significant levels of radioactivity present in plasma. The relative stability of the [ 14 C]FA label was demonstrated by the retention for more than 12 h of an isotope ratio close to that of the compound administered. The 14 C label of DLPC remained in position‐2, as assessed by cleavage of plasma phospholipids with phospholipase A 2 . The [ 3 H]choline label showed an early incorporation into high density lipoproteins and subsequently into low density lipoproteins (LDL); conversely, the 14 C radioactivity was rapidly incorporated into triacylglycerols that were mainly associated with very low density lipoproteins. Radioactivity measurements revealed that both isotopes remained the longest time in LDL. In red blood cell (RBC) lipids, [ 3 H]choline radioactivity accumulated over time, with a plateau after 48 h, whereas FA radioactivity accumulated more rapidly and was followed by a progressive decay. Analysis of the isotope ratio in these cells suggested an early incorporation of lyso products followed by rapid transfer of FA from plasma. The RBC maintained considerable radioactivity for a prolonged time, thus acting as a possible reservoir for the DLPC administered. Our study showed that dilinoleoyl PC remained in plasma longer than predicted based on earlier studies, and that after absorption the FA label was found in position 2.